Microendoscopic observations of the hemodynamics in the rabbit ciliary processes

Funk, Richard; Wagner, Willis H.; Wild, Julia

doi:10.3109/02713689209001810

Cited by 15 publications

(22 citation statements)

References 14 publications

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“…This pattern of venous drainage is seen in other species [12]. The marginal capillaries may be responsible for the very high blood flow values compared to the choroid, kidney cortex and cardiac muscle [1] and blood flow velocities of the ciliary process [7]. This hemodynamics would be anticipated considering the ciliary process function secreting aqueous humor.…”

Section: Discussionmentioning

confidence: 80%

Microvascular Anatomy of the Pig Eye: Scanning Electron Microscopy of Vascular Corrosion Casts

Ninomiya

Inomata

2006

J. Vet. Med. Sci.

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ABSTRACT. The microvasculature of the eye of 10 pigs was investigated using scanning electron micrographs of corrosion casts. The ciliary body, iris and bulbar conjunctiva were supplied by the iridociliary ring artery via the long posterior ciliary artery. Capillaries of the ciliary process were of large diameter (23.2-27.5 µm) with an irregular bore, forming a thoroughfare channel draining blood in the ciliary arterioles into the pars plana venous vessels. Arterioles and venules in the iris exhibited a zigzag or spiral features. The third palpebra was supplied by the anterior ciliary artery. The capillary bed of the third palpebra was dense and was formed by many rows of fine hair-pin loops. Capillaries in the bulbar conjunctiva formed a sparse network disposing approximately parallel to the epithelium and formed a well-developed venous plexus, draining into the vortex veins. Retinal arterioles formed a slender and long course to capillaries. Retinal capillaries were extremely thin (3.0-4.0 µm in diameter). The choroid was supplied by the short posterior ciliary arteries.Choroidal arterioles exhibited a thick and short course to the choriocapillaris. The choriocapillaris was flat and sinusoid-like (8.9-13.9 µm in diameter), forming a dense sheet-like network. Blood from the choroid emptied into the episcleral vein via the vortex vein. Blood from the retina was drained by the posterior ciliary veins. The functional significance of this vascular architecture was discussed.

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Section: Discussionmentioning

confidence: 80%

Microvascular Anatomy of the Pig Eye: Scanning Electron Microscopy of Vascular Corrosion Casts

Ninomiya

Inomata

2006

J. Vet. Med. Sci.

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“…This pattern of venous drainage is also seen in other species [11]. The thick marginal capillaries may be responsible for the very high blood flow values found in comparison to those of the choroid, kidney cortex and cardiac muscle [1], and for the blood flow velocities in the ciliary process [5]. The thoroughfare channels may be the equivalent of arteriovenous anastomoses, wherein the blood in the pars plana venules is not truly venous blood, but rather highly oxygenated blood [5].…”

Section: Discussionmentioning

confidence: 54%

“…The thick marginal capillaries may be responsible for the very high blood flow values found in comparison to those of the choroid, kidney cortex and cardiac muscle [1], and for the blood flow velocities in the ciliary process [5]. The thoroughfare channels may be the equivalent of arteriovenous anastomoses, wherein the blood in the pars plana venules is not truly venous blood, but rather highly oxygenated blood [5]. The present SEM observation of the corrosion casts of the rabbit eye revealed the frequent occurrence of intra-arterial cushions at the branching sites in the retinal and choroidal arterioles, as seen in other organs [7].…”

Section: Discussionmentioning

confidence: 99%

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Microvascular Architecture of the Rabbit Eye: A Scanning Electron Microscopic Study of Vascular Corrosion Casts

2008

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ABSTRACT. The microvasculature of the eyes of 5 rabbits was investigated using scanning electron microscopy on corrosion casts. The study revealed that the pars plana vessels draining blood from the iris and ciliary body coursed directly into the anterior vortex venous system constituting the scleral venous plexus (the venous circle of Hovius). The episcleral vasculature was found to possess a specialized morphology, with channels draining the aqueous humor. The capillaries of the third palpebral, bulbar and palpebral conjunctiva formed a single-layered capillary network approximately parallel to the epithelium and formed a well-developed venous plexus in the stroma. The retina was found to be merangiotic, meaning that vessels were present only in a small part of the retina, extending in a horizontal direction to form bands on either side of the optic disc. Channels representing the aqueous veins that drained blood mixed with aqueous humor were found to derive directly from the suprachoroidal space and communicate with the scleral venous plexus via the anterior vortex veins. The functional significance of the microvasculature of the iris, cilia, retina and choroid is discussed in this report as well. The elaborate microvasculature of the conjunctiva may be a prerequisite for the exchange of nutrients and gasses between the cornea and the vessels across the conjunctival epithelium when the eyelids are shut during sleep, and possibly for the dynamics of eye drop delivery. The scleral venous plexus in rabbits may be analogous to the scleral venous sinus (Schlemm's canal) in rats, primates and humans.

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“…The thick marginal capillaries may be responsible for the very high blood flow values that are seen as compared to the choroid, kidney cortex and cardiac muscle, and the blood flow velocities of the ciliary process [6]. This bypass of the capillaries may allow for a large amount of arteriovenous shunt volume, in which the blood in the pars plana venules is not truly venous blood, but rather highly oxygenated blood.…”

Section: Discussionmentioning

confidence: 99%

Microvasculature of the Retina, Ciliary Processes and Choroid in the North American Raccoon (Procyon lotor) Eye: A Scanning Electron Microscopic Study of Corrosion Casts

Ninomiya

Inomata

Kanemaki

2005

The Journal of Veterinary Medical Science

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ABSTRACT. We have studied the vasculature of the retina, ciliary processes and choroid in the North American raccoon (Procyon lotor), a nocturnal mammal, using light and scanning electron microscopic examination of corrosion casts. We carried out an identical study in the crab-eating macaque (Macaca fascicularis), which forages only during the daytime, in order to compare the ocular vasculature with that of nocturnal mammals. Our observations in raccoons demonstrated a photoreceptor layer associated with rich lymph and a poorly vascularized retina. The meridian region of the eye, which lies in the horizontal plane and pass around the optic disc, had a markedly sparse capillary network. This horizontal sparse vascular band may correspond to a visual streak. Ciliary process capillaries were delicate, and formed a well-developed and compact network. Choriocapillaries were quite thin and formed a coarse capillary network. This contrasted with the dense retinal and well-extended choroidal capillary networks noted in the macaques. Our findings suggest that the sparse retinal capillary network in raccoons is extremely beneficial for photon capture, thereby allowing the raccoon to see well at night, as the retinal vessels restrict the inflow of photons toward the photoreceptors. The well-developed lymph probably compensates for the sparse retinal capillaries and choriocapillaries and nourishes the retina in the nocturnal raccoon. KEY WORDS: corrosion casts, eye, raccoon, SEM, vasculature.J. Vet. Med. Sci. 67(6): 547-554, 2005 The North American raccoon (Procyon lotor) is a mammalian nocturnal omnivore that is found throughout most of the United States. Recently, they have also been found to be present throughout most of Japan. They were initially imported as pets but due to an increase in escaped or abandoned animals, their numbers have grown over the past decade, especially in urban and suburban areas. Raccoons cause a variety of problems, including feeding on dog or cat food, feeding on trash in garbage cans, establishing dens in attics or wall spaces, and/or causing damage to vegetable gardens. The raccoon is widely known for its habit of "washing" its food in water. The species name, lotor, actually means "the washer" in Latin. The animal has a very well-developed sense of touch, but its vision is not very good. The behavior in which they dunk their food in water looks like washing and is referred to as "dabbling". However, this "washing" of food items more than likely helps to enhance their sense of touch and assist them in finding food underwater through the use of their sensitive paws and digits. This action also enables them to sort out items that are not edible. Another nocturnal animal, the vizcacha (Lagostomus maximus maximus) [11], has an avascular retina, and rabbits [23], guinea pigs [19] and horses [19] are known to have poorly vascularized retinas. However, information on the vascular system of the raccoon eye has not been previously reported. Our study presents the results of light and scanning elect...

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Microendoscopic observations of the hemodynamics in the rabbit ciliary processes

Cited by 15 publications

References 14 publications

Microvascular Anatomy of the Pig Eye: Scanning Electron Microscopy of Vascular Corrosion Casts

Microvascular Anatomy of the Pig Eye: Scanning Electron Microscopy of Vascular Corrosion Casts

Microvascular Architecture of the Rabbit Eye: A Scanning Electron Microscopic Study of Vascular Corrosion Casts

Microvasculature of the Retina, Ciliary Processes and Choroid in the North American Raccoon (Procyon lotor) Eye: A Scanning Electron Microscopic Study of Corrosion Casts

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